Phytochemical exploration of halophytic plants and valorization for the formulation of a bioinsecticide

Abstract

This study aimed to investigate the phytochemical profile and evaluate the antioxidant and insecticidal activities of leaf methanolic extracts from three Algerian halophytes: Atriplexhalimus, Limbardacrithmoides, and Suaedafruticosa. Phytochemical screening was conducted to detect major secondary metabolites, along with the quantification of total phenolic, flavonoid, and tannin contents using the Folin–Ciocalteu, aluminum chloride, and vanillin assays, respectively. ATR-FTIR spectroscopy was used to identify functional groups, while HPLC-ESI-QTOF-MS analysis provided a detailed characterization of the phytochemical constituents. Antioxidant activity was evaluated using DPPH, ABTS, and FRAP assays. Insecticidal activity was assessed through direct contact bioassays at four concentrations (25, 50, 100, and 200 mg/mL) against Triboliumconfusum, as well as repellency and plant powder toxicity tests. Finally, molecular docking studies targeting acetylcholinesterase (AChE) were performed to identify potential bioactive compounds responsible for the observed biocidal effects. The phytochemical screening results revealed the presence of major bioactive constituents in all extracts, while FTIR analysis confirmed their characteristic functional groups. S. fruticosa exhibited the highest levels of total phenolics and tannins (119.33 ± 7.24 mg GAE/g DW and 4.51 ± 0.09 mg CE/g DW, respectively), whereas A. halimus showed the highest flavonoid content (73.07 ± 0.19 mg QE/g DW), and L. crithmoides recorded the lowest values. These results were consistent with the observed antioxidant and insecticidal activities. Indeed, S. fruticosa showed the strongest antioxidant activity, with the lowest IC₅₀ values for DPPH (0.48 ± 0.001 mg/mL) and ABTS (1.03 ± 0.006 mg/mL), as well as the highest FRAP value (2130.96 ± 2.55 μmol Fe²⁺/g DW), followed by A. halimus and L. crithmoides. Similarly, insecticidal assays revealed the lowest LC50 value (50.03 ± 12.65 mg/mL after 96 h of treatment) compared with A. halimus (84.73 ± 0.00 mg/mL) and L. crithmoides (88.86 ± 17.52 mg/mL). HPLC-ESI-QTOF-MS analysis in negative ion mode led to the identification of 24, 27, and 29 bioactive constituents in A. halimus, L. crithmoides, and S. fruticosa, respectively, including compounds such as kaempferol 3-O-rutinoside-7-O-glucoside, naringin, feruloyltyramine, rutin, dicaffeoylquinic acid, quercetin 3-O-glucoside, chlorogenic acid, and 3-O-feruloylquinic acid. Molecular docking studies further showed that these compounds exhibited strong binding affinity toward insect acetylcholinesterase (AChE).